A multiple purpose industrial tractor having at least one vertically adjustable support arm can be provided with a tool adaptor on the outer end of the arm to permit the rapid attachment or detachment of a tool, e.g. a loader bucket assembly. In many models, the tool is attached to the tool adaptor by an element on the top of the tool mating with an element on the top of the adaptor and by one or more hydraulically actuated locking pins extending into engagement with corresponding openings in the frame elements on the tool.
The hydraulically actuated cylinders can be either continuously connected by suitable hydraulic conduits to a hydraulic system on the vehicle chassis or they can be provided with quick disconnect fittings which permit their connection to a hydraulic fluid supply system for the short periods of time necessary to accomplish assembly or disassembly. In the continuous connection embodiment, the hydraulic conduits to the locking cylinders are subject to the risk of being damaged during operation of the equipment, and the loss of fluid in the locking cylinders can result in the tool becoming unlatched from the tool adaptor. Similarly inadvertent giggling of a single operating multi-function lever by the operator could cause the locking pins to be moved to their unlocked position in the situation where the locking pin cylinders are continuously connected to the vehicle hydraulic system.
The use of quick disconnect fittings adjacent to the locking cylinders and the removal of the hydraulic supply conduits from those fittings except when needed can eliminate the damage risk associated with long supply conduits extending to the locking cylinders during the operation of the tractor. However, the use of the quick disconnect fittings also have attendant problems. For tools which have hydraulically operated elements, it is common to position the tool on the tool adaptor, connect the hydraulic fluid supply conduits to the quick disconnect fittings for the locking pin cylinders to move the locking pins into locking engagement with the tool, disconnect the hydraulic fluid supply conduits from the quick disconnect fittings for the locking pin cylinders and then connect the hydraulic fluid supply conduits to the quick disconnect fittings for the hydraulically operated elements on the tool. During disassembly of such tools from the tool adaptor, the reverse procedure is necessary. Such use of quick disconnect fittings involves multiple steps and also the risks of disruptions to the hydraulic circuits.
In both the continuous connection embodiment and the quick disconnect fitting embodiment, the inclusion of locking cylinders in the primary hydraulic circuits for the vehicle can cause problems in providing adequate capacity for all of the hydraulically actuated elements and in preventing surging in one element from interfering with the operation of another element. In addition, the vehicle must be in an active operational state in order to have the hydraulic fluid pressure available to operate the locking pin cylinders.